Radiographic cameras such as those disclosed in the U.S. Pat. No. 3,011,057 which issued in the name of H. O. Anger on Nov. 28, 1961, or the U.S. Pat. No. 3,914,611 which issued in the name of K. J. Stout on Oct. 21, 1975, employ a scintillator, a collimator and a detector. The collimator is positioned between a radioactive subject and the scintillator for guiding quanta of radiation towards the scintillator. The scintillator produces optical photons in response to the incident radiation which may be gamma radiation or X-radiation. The detector is responsive to the optical photons for signalling the sites of impingement of quanta of the radiation within the scintillator whereby an image of the radioactive subject is obtained. A construction feature frequently utilized in the building of such radiographic cameras is a mirrored surface applied to the front face of the scintillator, as by silvering the front face, so that optical photons produced by the scintillations and radiated back towards the front face in the direction of the subject are reflected by the mirrored surface away from the subject and towards the detector. The mirrored surface is useful in increasing the intensity of light from the scintillations to produce an optical signal that is more readily detected by the detector.
A problem arises in that radio pharmaceuticals injected into, or ingested by, the subject for producing an image thereof result in greater efficiencies of the scintillator at the higher energies of the foregoing radiation; the higher energy radiation inducing greater numbers of optical photons per quanta of incident radiation than is produced by the lower energy radiation. However, in order to accommodate the higher energy radiation the scintillators are made increasingly thick, the thickest scintillator being utilized with the highest energy radiation in order that the scintillator be able to absorb enough radiation for the scintillations. The scintillations produced by the high energy radiation occur within substantially greater regions from the front face of the scintillator with the result that optical photons of a scintillation which reflect off the mirrored front face of the scintillator travel on paths that are substantially displaced from, and angled to, a direct path of propagation from a site of the scintillation to the detector. As a result, the detector sees an enlarged area from which optical photons appear to be emanating when, in fact, the photons emanate from a substantially smaller region at the site of the scintillation. Furthermore, in the case of gamma radiation propagating along paths inclined relative to the scintillator as occurs with converging, diverging, or pinhole, collimators, the scintillations produced near the front face of the scintillator are laterally displaced relative to scintillations produced near the back face of the scintillator even though all of the scintillations may result from radioactive events at a common point of the subject. The lateral displacement of scintillations blurs the images of points of the subject. Thus, the advantages associated with the high scintillator efficiencies at the higher energies may be outweighed by the disadvantages of a lowered resolution capability of the radiographic camera, the lowered resolution capability being due to the apparent increase in the region from which the optical photons of a scintillation appear to emanate as well as the lateral displacement of scintillations identifying a single point of the subject.